550 Repoet of the State Geologist. 



ated and subacute basal extremity ; substance thin ; external 

 characters of zooecia as in Khombopora. ; primitive portion short ; 

 hemisepta well developed." (Ulkioh.) 



Rhombopora, Meek. 



(Pal. Eastern Nebraska, p. 141.) 



Type, Ehombojpora lepidodendroidea^ Meek. 



(Plate 19, figs. 10-13.) 



Zoarium ramose, solid; cells cylindrical, radiating from an 

 imaginary axis ; tabulate ; cell apertures disposed in straight 

 longitudinal rows or in diagonally intersecting rows. In 

 the former case the rows are generally separated by promi- 

 nent ridges ; in the latter the interapertural surface consists 

 of rhombodial or polygonal elevations surrounding the aper- 

 tures. Usually nodes or short spines occur between the cell 

 apertures. The intercellular space near the surface is occupied 

 by tubuli formed by the growth of the interapertural nodes. 



Trematella, Hall. 



(Rep. of IS". Y. State Geologist for 1886, advance sheets.) 



Type, Trematella annulata, Hall. 



(Plate 19, figs. 6-9.) 



The internal character is similar to that of Rhombopora, but 

 the cells are more closely disposed and the intercellular space is 

 generally solid ; but sometimes the spiniform tubuli occur. The 

 apertures are more closely arranged in a somewhat quincunx 

 order, surrounded by polygonal elevations. The monticules are 

 elongated laterally and are so disposed as to give to the branches 

 an annulated appearance. This peculiar disposition of the mon- 

 ticules has been observed in all the species of the genus. 



Family Streblotrypidae, Ulrich, emend. 



The forms included in this family are very similar to the 

 Rbomboporid^, but they have in the peripheral portion intercel- 

 lular tubuli and interapertural polygonal pits. 



